Container Control not keeping focus - other buttons appear

using 2015r2.1 on Win7

I have a ContainerControl in my app. and have added the container control to a window in the IDE with Ctrl-Drag. Any changes I make to the Super Control are also changed in the control in the Window. So far - so good.

I then open a new instance of the window.

The ContainerControl is hidden ( left property is a negative value of .left = 0 - ccon1.width ) and when the mouse is moved over a rectangle shape, the left property changes to 0, to bring the ContainerControl into view ( like a tab of controls and settings options that slide in from the edge of the window ).

Problem is that when I move the mouse around the control, the buttons from the window ( behind the container control ) are suddenly appearing in front of the control.

Does not seem to happen with SegmentedControl, Labels or TextArea controls.

Suggestions please.

OK. Seems like it is not just the ContainerControl.

Same thing happens if I use a Canvas or a PagePanel.

Do I need to disable each of the controls on the Window first ?

OK. I think I have a workable solution to this.

I have added a Window3 ( Floating Window ). This stops the other controls on Window1 from appearing.
Added a property to Window1 : winID
Added a property to Window3 : OwnerID

When a new instance of Window1 is created, I check all existing instances of Window1, and get the highest winID integer value.
Add 1 to get the next ID number.
Set the new Window1 instance winID to the new value.

When I click to open an instance of Window3, the Window1 sets the Window3 property ( OwnerID ) to the same as Window1.winID.
I can then set the position of the new Window3, relative to the position of the instance of Window1.

When Closing Window3, reads the OwnerID integer value, loops all the open instances of Window1, and when the same ID is found, then updates the data on correct instance of Window1.